Rep. Rob Wittman said, citing a hardware integration glitch that has spilled over into the acceptance and fielding of some new F-35s, that the APG-81 is unlike the APG-85, and thus delivering the plane, as now designed, with an APG-85 radar, rather than an APG-81 radar.
The problem involves the Production Lot 17 aircrafts that were meant to contain the AN/APG-85, a next generation active electronically scanned array radar, supposed to replace APG-81 as the fire-control standard of the F-35 to the services of the U.S. Rather, there has been a mismatch in the new radar and structural mounting points of the forward fuselage that existed during the construction of airframes on APG-85 provisions. That apparently humble engineering fact has had disproportionate implications on the functioning of the aircraft since the nature of the F-35 design, the radar is not an optional add-on, but rather a core part of a fused sensor-and-effects system.
Practically, the F-35 will not be “blind’ without its radar. The jet continues to have passive sensing on board with the Distributed Aperture System and Electro-Optical Targeting System, and it is also able to ingest the tracks of other platforms on secure data links. However, by lack of onboard AESA radar, a significant aspect of autonomous search, targeting and electronic attack is eliminated. Networked sensing can conceal the deficiency in formations and maneuvers, the plane can fly with other F-35s equipped with radars and share the same tracks. This has been shown to be limited when the aircraft has to create its own image, shoot down targets without any satellite assistance, or share radar power as a component of an organised electronic-warfare strategy. In the case of a fighter sold and acquired as a sensor-fusion platform, the divide does not lie cosmetically.
Wittman went to the mechanical cause of the problem: The bulkhead configuration is central as both of the radars are extremely different… the “attitude” of the array it makes all the difference in the world how the radar works. That attitude is not a point of discussion; it represents very narrow tolerances in the way an electronically steered array has to be oriented to fit performance requirements and remain consistent with the nose geometry of the aircraft. The reports associated with Lot 17 deliveries have also reported of aircrafts relying on nose ballast in order to maintain balance in the event that the intended radar is not installed, a measure that keeps the airframes flyable yet the combat system is not complete.
The F-35 overall modernization bottleneck is also connected to the engineering pressure behind APG-85. The radar is often linked to gallium nitride equipment to make it more efficient and power dense, and Wittman wrote in an 82 kilowatts of power to run the more aggressive array. That need is directly linked to the propulsion and thermal-management modifications ongoing with the F135 engine, and it supports the main reason why a radar modification can trigger cooling, power allocation and software integration liabilities throughout the airplane.
The latter burdens are falling during Technology Refresh 3 and Block 4 burdens. TR-3 refers to the computing base that is to accommodate extended sensor processing and additional mission software and has already pushed the program into weird delivery schedules, such as accepting aircraft to limited role pending retrofit. The earliest scheduled completion of Block 4 by the GAO is 2031 and the critical capabilities are moved very far right as the production keeps growing in scale.
That is the main conflict that can now be seen through the door: the speed of procurement is to maintain the line running, whereas the full capability requires the components to come with the software maturity, and components-radar, computing, engine upgrades, etc. Wittman put the tradeoff in blunt words: I wish they could do it as quick as they can and get the system going. I do not want it shipped, when it will be operationally defective since that means the plane will remain at the tarmac.
In the case of the F-35 enterprise, the radar integration issue is not so much a box-which-is-not-there as it is the manifestation of how the fifth-generation upgrades interact with the physical architecture, test time and the realities of fleet-wide configuration management. The plane does not go dead, the plane is still a plane, it can share information, but the promise of the program has always been that every jet is a high end sensor itself- not merely a node waiting to be filled in by another planes radar picture.
